Retinal degeneration is a major characteristic of retinitis pigmentosa (RP), age-related macular degeneration (AMD), autoimmune retinopathy (AR), and other related retinal diseases. The common end outcome of all forms of degenerative diseases is photoreceptor cell death and loss of visual function. As photoreceptors degenerate, secondary changes, including vascular leakage, exacerbate visual loss leading to blindness (Milam et al., Prog. Retin. Eye Res. 17:175-205, 1998; Grunwald et al., Am. J. Ophthalmol. 122:502-508, 1996). The mechanism leading to development of these diseases remains largely unknown and appears to be complex, likely caused by combinations of genetic and cellular factors that affect not only the disease itself but also its response to various treatments (Nussenblatt and Ferris, Am. J. Ophthalmol. 144:618-626, 2007; Reme et al., Documenta Ophtholmologica 106:25-29, 2003).
Treatment options for these conditions remain limited. Currently, the therapeutic approach is restricted to slowing down the degenerative process by sunlight protection and vitamin therapy, treating complications (such as cataract and macular edema), and helping patients to cope with the social and psychological impact of blindness. Gene therapy has been shown to be effective in a few RP patients with specific gene mutations, but there is no effective therapy that stops the development of the disease or restores the vision, so the visual prognosis is poor. At present, the most effective proven therapy for AMD is repeated intravitreal injection administration of humanized antibodies against vascular endothelial growth factor (VEGF); however, such injections have a high risk of complications.
Optic neuritis is an inflammation of the optic nerve. This condition usually presents with sudden onset of vision loss, typically in one eye. Other symptoms include pain on eye movement, altered color vision, and decreased pupillary light reaction. Recovery of visual acuity generally occurs over a period of weeks to months; however, color vision, contrast sensitivity, and light brightness sensitivity abnormalities may persist. Treatments for optic neuritis vary depending on the specific etiology, but corticosteroids are often effective.